Disabling an email account

How can a particular email account be ‘disabled’ temporarily. Note that the email account should not be ‘deleted’ ? Is this possible at all via cPanel?

There is no direct functionality in cPanel at the moment for this. This feature might be added at a later stage.
However, you can achieve this functionality by modifying a few entries via SSH.

Comment out the entries related to the particular email account in the following locations:
/home/user/etc/domainname/passwd
/home/user/etc/domainname/shadow
/home/user/etc/domainname/quota

Make sure that you just comment them and NOT delete them as you might need them back later.